223-4 Evaluating Uplift of the Wood River Mountains, Southwestern Alaska, using Apatite and Zircon (U-Th)/He Thermochronology and Scarp Mapping

Session: Rock Deformation and the Dynamics of Mountain Building: A Session Honoring the Scientific Contributions of John P. Platt (Posters)

Presenting Author:

Authors:

Abstract:

The active right-lateral strike-slip Denali fault is associated with elevated terrain along its ~2500 km length from British Columbia to western Alaska. One location of understudied elevated terrain is the Wood River Mountains in southwestern Alaska. These mountains are spatially associated with a restraining bend in the NE-SW-striking Denali fault and its intersection with the N-S striking Aniak fault to the north. These strike-slip faults intersect at an acute angle and, owing to their contrasting kinematics, create a “zipper fault” junction. Whereas the fault kinematics and timing of slip are generally known, it remains unclear how the mountains formed and if their exhumation history is a signature of Denali-Aniak fault zippering. This research aims to bracket the timing of topographic uplift in relation to displacement along the Denali and Aniak faults. We test the hypothesis that the Wood River Mountains were uplifted due to the creation of a restraining bend along the Denali fault, which was caused by converging crustal blocks in response to left-lateral displacement along the Aniak fault to the north. To investigate this hypothesis, we will use forthcoming (U-Th)/He dating of apatite and zircon to determine when the rocks cooled through upper crustal temperatures and remote mapping of fault scarps to determine how the faults have reorganized since restraining bend formation. A Late Cretaceous unconformity preserved at the margins of the range will be used along with the thermochronology dates to bracket net surface uplift since ca. 70 Ma. The thermochronology sampling strategy employed a series of glacial finger lakes, which provide data along three spaced transects oriented across strike from the Denali fault. The results from this study will provide the first modern thermochronology from the Wood River Mountains, the locations of structures associated with topographic development of the mountains, and a tectonic model that incorporates the uplift in the context of regional fault kinematics and related block motions.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9674

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